Imaging scans including inhaled noble gas magnetic resonance imaging show promise over forced expiratory volume tests (FEV1) in evaluating symptoms of patients' with chronic obstructive pulmonary disease (COPD) and exercise limitations, according to a study published online July 7 in Radiology.

“FEV1 doesn't tell the whole story,” coauthor Grace Parraga, PhD, from Imaging Research Laboratories, Robarts Research Institute, and the Department of Medical Biophysics at the University of Western Ontario, London, Canada, said in a news release. Symptoms and exercise capacity can vary wildly in patients with only slightly abnormal FEV1.

Miranda Kirby, PhD, from the James Hogg Research Centre, the University of British Columbia, and the Institute of Heart and Lung Health, St Paul’s Hospital, Vancouver, Canada, and colleagues investigated whether airway measurements taken with magnetic resonance imaging and computed tomography (CT) scans could predict symptoms more accurately than FEV1.

The participants were 116 people with COPD who were between the ages of 50 and 85 years and had a smoking history of at least 10 pack-years. Most (80 participants) had mild to moderate COPD (defined as Global Initiative for Chronic Obstructive Lung Disease grade II).

In multivariate modeling, the investigators found that for the 36 patients with severe COPD, FEV1 predicted how they would perform on a 6-minute walk test (β, 0.48; P = .01). However, for the 80 participants with mild to moderate COPD, FEV1 did not meaningfully predict their performance. Instead, the useful measurements were hyperpolarized helium apparent diffusion coefficient (β, 0.34; P= .04), diffusing capacity of the lung for carbon monoxide (β, 0.60; P = .0008), and residual volume/total lung capacity (β, −0.26; P = .02).

To predict symptom scores on the St George's Respiratory Questionnaire in patients with mild to moderate COPD, the significant variables were hyperpolarized helium apparent diffusion coefficient (β, 0.60; P = .005), relative area of the CT attenuation histogram with attenuation of −950 HU or less (β, −0.52; P = .02), and FEV1 (β, −0.45; P = .0002). Among those with more severe COPD, apparent diffusion coefficient was the most significant (β, 0.95; P = .01), followed by relative area of the CT attenuation histogram with attenuation of −950 HU or less (β, −0.62; P = .07) and CT airway count (β, −0.49; P = .01).

“In patients with mild-to-moderate COPD, [magnetic resonance] imaging emphysema measurements played a dominant role in the expression of exercise limitation, while both CT and [magnetic resonance] imaging measurements of emphysema explained symptoms,” write Dr Parraga and colleagues.

“Our findings suggest that pulmonary imaging measurements have the potential to provide important information about mild COPD, and this supports a role for MR imaging and CT as platforms for COPD research and clinical care,” write Dr Parraga and colleagues. They note that techniques not used in their study, including CT perfusion imaging and dual-energy CT, may also be valuable for this purpose.

One coauthor has received honoraria from AstraZeneca, Takeda, Almirall, and Amgen and has received grants from Boehringer Ingelheim and Novartis. Another coauthor is a consultant for GlaxoSmithKline and has grants pending with GlaxoSmithKline and Spiration. The other authors have disclosed no relevant financial relationships.